1. Field of the Invention
The present invention relates to a variable stroke engine having a connecting rod with one end thereof connected to a piston via a piston pin, a sub-rod connected to a crankshaft via a crankpin and to the other end of the connecting rod, and a control rod with one end thereof connected to the sub-rod at a position distal from the position where the connecting rod is connected. In particular, the present invention relates to a variable stroke engine also having an eccentric shaft connected to the other end of the control rod, wherein the eccentric shaft is provided at a position eccentric relative to a rotating shaft to which power is transmitted from the crankshaft at a reduction ratio of ½.
2. Description of the Related Art
Conventionally, such a variable stroke engine is known, such as, for example, the engine disclosed in U.S. Pat. No. 4,517,931 to Nelson.
In the case of a DOHC or SOHC variable stroke engine, rotational power is generally transmitted from the crankshaft to a camshaft supported on a cylinder head at a reduction ratio of ½ using a timing belt and the like. In the case of an OHV variable stroke engine, a camshaft is generally provided to which power is transmitted from the crankshaft at a reduction ratio of ½ by a reduction gear, in addition to a rotating shaft, to which power is transmitted from the crankshaft at a reduction ratio of ½.
It is therefore necessary in conventional DOHC and SOHC variable stroke engines to provide space for the camshaft above the cylinder head, which results in an increase in the overall dimensions of the engine. In the conventional OHV variable stroke engine, a reduction gear positioned between the crankshaft and the camshaft causes mechanical noise, and the overall complicated structure of the engine increases friction loss.